Location systems generally are very well known, and mostly nowadays use GPS systems interconnected with communications systems to broadcast location data on a periodic, continuous or on an ad-hoc basis.
Location systems are used in a great many situations ranging from relatively mundane applications, such as vehicle tracking (for example, in the logistics industry to monitor the locations of vehicles and payloads); to more critical applications, such in as search and rescue operations (for example, in distress beacons for locating ships or aircraft).
In all known cases, the basic principle of operation of the location device is largely the same, that is to say, the system ascertains its position (for example, using GPS), and broadcasts its position (for example, using a Public Wireless Mobile Telephony Network (PWMTN), a satellite phone link, VHF radio signaling, etc.) to a remote receiving station. The received position data can then be processed by the remote receiving station in a variety of ways, such as by placing markers on maps, generating alerts, deploying resources, etc.
Examples of known location systems, such as those described above, are known from the following:
US 2014/167955A discloses a system for allowing a master device to locate a plurality of slave devices, wherein the system may be used in an emergency, may trigger an alarm via a cellular communication network and may locate the position of each slave device on a map via GPS. However, this document does not teach using short-range wireless communications between the slave units and using a daisy-chain of signals to relay the locations of other in-range slave units to other slave units and then to the master unit.
KR 2006/0131182A discloses a system involving GPS for alerting the user of a mobile terminal if they exit a safety zone, and may further involve alerting of a guardian. Here, the communications are all long-range, i.e., over a PWMTN and there is no disclosure of daisy-chaining signals enabling the use of short-range, and hence low-power, signals.
US 2005/143096A discloses a system for monitoring the location of group members providing an indication of when the user nears a perimeter such as in the form of a graphical display and may sound an alarm. However, each mobile phone connects directly to the master unit, rather than communicating with their nearest neighbors.
US 2008/268830A discloses a system for proximity detection of coverage area boundary that may provide the user with a visual indication and audio warning of boundary location. This is essentially an in-bounds/out-of-bounds system with no direct relevance to this disclosure.
EP0921411A discloses a system for monitoring boats involving the use of a GPS and a public telephone network to report ships' positions in an emergency. This system relies solely upon long-range communications.
CN103178616A discloses a wireless positioning system with forbidden zone management that may send out an alarm signal if workers are in the zone.
US 2013/084973A discloses a system for providing proximity based alerts to a wireless device associated with a user.
CN202815226U discloses a terminal that allows the user to monitor the location of students via the use of GPS and a GPRS network communication module that may allow for the monitoring of students outside security zones.
WO 11082208A discloses an animal monitoring system involving a communication device and tags for sensing and triggering if an animal crosses a physical zone or boundary.
WO 09035760A discloses a system for alerting a user of a mobile device of the proximity of a target party, wherein the alert may include map data.
GB2459880A discloses a system for monitoring workers via a wireless network, wherein users may receive a warning if they enter a safety zone.
KR100617149B discloses a system for indicating to the user that they are leaving a predefined area, involving the use of GPS, mapping information and text messaging.
WO 0251193A discloses a system that may generate an action when a mobile station approaches a boundary.
It will be appreciated from the foregoing that known locations systems work very well, but in certain applications, there can be problems:
First, known location systems such as those described above utilize long-range communications systems to broadcast the location data to the remote monitoring station. This has several practical implications, such as using relatively large amounts of power, which limits how long such systems can operate using relatively small batteries. Thus, miniaturization of known battery-powered location systems is restricted by power requirements, often meaning that a trade-off needs to be struck between miniaturization and duty cycle.
Second, known location system such as those described above broadcast data over public telephony or communications networks. This means that there is a potential for data broadcasts to be misdirected (leading to potential security breaches) and for false alarm signals to be sent to emergency services, which can result in unnecessary deployment of emergency services resources. Also, in certain situations (for example, tracking people or items inside a building or within a limited perimeter), there is no need for a connection to the “outside world,” so the use of public/external communications is contraindicated.
Third, broadcasting data over public communications networks often requires a license or a subscription fee to be paid (e.g., for use of the communications network), which can be uneconomic for some users.